Biochemical characterization of microalgal biomass from freshwater species isolated in Alberta, Canada for animal feed applications

Abstract

Biochemical composition of freshwater microalgae isolates from Alberta, Canada was determined. Growth rate (0.98±0.07d−1), biomass production (0.35±0.03gDWL−1) and daily productivity (0.14±0.01gDWL−1d−1) were the same for Chlorella vulgaris (AB02-C-U-BBM), Nannochloris bacillaris (AB03-C-F-PLM), Tetracystis sp. (AB04-C-F-PLM02) and Micractinium reisseri (AB05-C-U-BBM02). Whole algal biomass (WAB) contained low ash (~2g100gDW−1) and protein (13–15g100gDW−1), high esterifiable lipid (32–36g100gDW−1), carbohydrate (27–30g100gDW−1) and energy (26–28MJkgDW−1). Oil fractionation was relatively ineffective for C. vulgaris and M. reisseri while oil was effectively extracted from N. bacillaris and Tetracystis sp. Accordingly, lipid-extracted biomass (LEB) from N. bacillaris and Tetracystis sp. contained higher protein (22g100gDW−1) and carbohydrate (43–44g100gDW−1) and lower residual esterifiable lipid (6–9g100gDW−1) than C. vulgaris and M. reisseri at 17–18g100gDW−1 (protein), 34–36g100g−1DW (carbohydrate) and 28–32g100gDW−1 (residual esterifiable lipid). Biomass had favorable essential amino acid (EAA) profiles with high EAA indices (0.9–1.1); rich in first-limiting EAA lysine (0.9–1.5g100gDW−1). Fatty acids (% of total) were predominantly monounsaturated fatty acids (MUFA; 40–53%), high in polyunsaturated fatty acids (PUFA; 27–40%) and low in saturated fatty acids (14–24%). N. bacillaris and Tetracystis sp. were particularly rich (9–12%) in α-linolenic acid (18:3n−3), had attractive n−3:n−6 ratios (0.5–0.7:1), were rich in iron (800–1616mgkgDW−1), had attractively low Ca:P ratios (0.6–0.9:1) and were virtually absent of contaminating heavy metals.